Understanding Circuit Breaker Markings 

By on

schneiderNSXNamePlate
Typical Circuit Breaker Nameplate
IEC 60947 is the circuit breaker standard and covers the marking of breakers in detail.  Any manufacturer following this standard should comply with the markings.

Name Plate and Breaker Markings

The illustration shows a standard nameplate from a Schneider NSX circuit breaker.   Other manufacturers should have similar information on the breaker.  The standard requires the following by information to be identified and marked on the circuit breaker.

Visible and legible when breaker installed:

  • rated current (In)
  • suitability for isolation, if applicable
  • indication of the open and closed positions

Marked, but need not be visible when installed:

  • manufacturer's name or trade mark and circuit breaker type designation or serial number
  • manufacturing standards the breaker complies with
  • utilization category
  • rated operational voltage (Ue)
  • rated impulse withstand voltage (Uimp)
  • rated frequency and/or the indication d.c.
  • rated service short-circuit breaking capacity (Ics) at corresponding rated voltage (Ue)
  • rated ultimate short-circuit breaking capacity (Icu) at corresponding rated voltage (Ue)
  • rated short-time withstand current (Icw), and associated short-time delay (for utilization category B)
  • line and load terminals (unless their connection is immaterial)
  • neutral pole terminal, if applicable ( by the letter N)
  • protective earth terminal, where applicable, by symbol
  • reference temperature for non-compensated thermal releases, if different from 30 °C

Additional Circuit Breaker Information

In addition to the above the following should be either marked on the circuit breaker or made available in technical documentation:

  • rated short-circuit making capacity (Icm)
  • rated insulation voltage (Ui),
  • pollution degree if other than 3
  • conventional enclosed thermal current (Ithe) if different from the rated current
  • IP Code, where applicable
  • minimum enclosure size and ventilation data (if any) to which marked ratings apply
  • details of minimum distance between circuit-breaker and earthed metal parts for circuit breakers intended for use without enclosures
  • suitability for environment A or environment B, as applicable
  • r.m.s. sensing, if applicable

Auxiliary Devices

Any auxiliary devices should be marked or technical information provided with the following:

  • rated control circuit voltage and frequency of any closing
  • rated control circuit voltage and frequency of any shunt release and/or under-voltage release
  • rated current of indirect over-current releases
  • number and type of auxiliary contacts and rated frequency
  • rated voltages of auxiliary switches (if different from those of the main circuit)

Symbols

The standard identifies the following symbols in connection with circuit breaker markings:

IEC60947Symbols

 

  Hopefully now, the next time we look at a break it should all make sense.



Steven McFadyen's avatar Steven McFadyen

Steven has over twenty five years experience working on some of the largest construction projects. He has a deep technical understanding of electrical engineering and is keen to share this knowledge. About the author

myElectrical Engineering

comments powered by Disqus



Low Voltage Fault Tables

The following tables provide quick order of magnitude fault levels for a a range of typical low voltage situations.

ANSI (IEEE) Protective Device Numbering

The widely used United Sates standard ANSI/IEEE C37.2 'Electrical Power System Device Function Numbers, Acronyms, and Contact Designations' deals with...

UPS Battery Sizing

Various techniques exist to enable the correct selection of batteries for UPS applications.  The procedure described below is one of the more common. ...

Wiki Depreciation

We have had the Wiki with us for a long time now, but at last I have decided to say bye bye – more details on why below.

Bows and Arrows

It starts with me reading one of the Horrible History books with my son (Groovy Greeks). Arrows were mentioned which lead to the discussion of the bodkin...

Calculating Cable Fault Ratings

When selecting a cable, the performance of the cable under fault conditions is an important consideration. It is important that calculations be carried...

How Electrical Circuits Work

If you have no idea how electrical circuits work, or what people mean then they talk about volts and amps, hopefully I can shed a bit light.  I’m intending...

Fire Resistant and Fire Retardant Cables

Fire resistant and fire retardant cable sheaths are design to resist combustion and limit the propagation of flames. Low smokes cables have a sheath designed...

Tip – Latitude and Longitude on Large Scale Plans

If you are working on a large plan, get the real coordinates [latitude, longitude] for two or more points and add them to the drawing. That way you can...

International System of Units (SI System)

The International System of Units (abbreviated SI) is the world's most widely used system of units.  The system consists of a set of units and prefixes...

Have some knowledge to share

If you have some expert knowledge or experience, why not consider sharing this with our community.  

By writing an electrical note, you will be educating our users and at the same time promoting your expertise within the engineering community.

To get started and understand our policy, you can read our How to Write an Electrical Note